We have nearly completed the construction of a low frequency experiemental LODESR spectrometer. There are some potential advantages of carrying out in vivo EPR using the technique of Longitudinally Detected ESR (or LODESR). These include higher sensitivity for broad lines (such as those seen with carbon-based oxygen-sensitive paramagnetic materials) and increased depth of detection. This has involved the construction of a low-noise preamplifier and demodulator circuit. Final system testing and evaulation are in progress.